public class BinarySearchTree {
    static class TreeNode{
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int key){
            this.val=key;
        }

    }
    public TreeNode root;

    public void insert(int key){
        if(root==null){
            root=new TreeNode(key);
            return;
        }
        TreeNode parent=null;
        TreeNode node=new TreeNode(key);
        TreeNode cur=root;
        while(cur!=null){
            parent=cur;
            if(cur.val<key){
                cur=cur.right;
            } else if (cur.val>key) {
                cur=cur.left;
            }else {
                return;
            }
        }
        if(parent.val>key){
            parent.left=node;
        }else {
            parent.right=node;
        }
    }
    public TreeNode search(int key) {
        TreeNode cur = root;
        while (cur != null) {
            if (cur.val < key) {
                cur = cur.right;
            } else if (cur.val > key) {
                cur = cur.left;
            } else {
                return cur;
            }
        }
        return null;
    }
    public void remove(int key){
        TreeNode cur=root;
        TreeNode parent=null;
        while(cur!=null){
            if(cur.val<key){
                parent=cur;
                cur=cur.right;
            } else if (cur.val>key) {
                parent=cur;
                cur=cur.left;
            }else {
                move(parent,cur);
                return;
            }
        }
    }
    public void move(TreeNode parent,TreeNode cur){
        if(cur.left==null){
            if(cur==root){
                root=cur.right;
            } else if (cur==parent.left) {
                parent.left=cur.right;
            }else {
                parent.right=cur.right;
            }
        }else if(cur.right==null){
            if(cur==root){
                root=cur.left;
            }else if(cur==parent.left){
                parent.left=cur.left;
            }else {
                parent.right=cur.left;
            }
        }else {
            TreeNode TargetParent=cur;
            TreeNode Target=cur.right;
            while(Target.left!=null){
                TargetParent=Target;
                Target=Target.left;
            }
            cur.val=Target.val;
            if(TargetParent.left==Target){
                TargetParent.left=Target.right;
            }else{
                TargetParent.right=Target.right;
            }
        }
    }
}
